This invention relates to a container for pressurized liquid such as carbonated beverage and more particularly to such a container having a flexible inner bag.
Gassed liquid products such as beer in the keg contain a substantial amount of gas, such as carbon dioxide, dissolved in the liquid. This liquid is kept under pressure within a pressure resistant vessel to keep the liquid product from going flat due to outgassing of carbon dioxide and exposure of the liquid to air. In commercial establishments which dispense such carbonated beverages, carbon dioxide or the like is supplied to the container through pressure-regulated tanks of gas. The complexity and size of such a system is such as to render it uneconomical for home dispensing.
"Bag-in-box" containers are used to prevent air from contacting non-pressurized liquids such as still wine while it is being stored and dispensed. Such a container consists of a substantially impermeable bag, usually of metallized polyethylene, disposed within a box of cardboard or similar material, the bag being filled with wine and having a tap projecting through the box material so that the wine can be easily dispensed. The great advantage of such a container over a conventional bottle, carafe or the like is that the bag is made of flexible material so that as liquid is dispensed, the bag collapses by a corresponding amount, and no air is allowed to enter to cause oxidation of the liquid. Accordingly the bag-in-box packaging keeps the product fresh for an extended period.
Attempts have been made to extend bag-in-box packaging to pressurized liquids, particularly carbonated beverages such as beer and soft drinks, so as to achieve, in relation to these liquids, the above-mentioned advantages. However, when such liquids are filled into flexible bags within semi-rigid casings in the form of boxes, the latter have been found to bulge outwardly because of the pressure within the liquid. This is clearly unsatisfactory as it makes the overall container unstable. Perhaps low carbonated beverages such as low carbonated beer and lightly carbonated wine coolers can be packaged in conventional bag-in-box containers if they are well constructed and carefully handled; however, present day fully carbonated beverages, which can generate pressures on the order of 90 psi, cannot be packaged therein.
There is disclosed in U.S. Pat. No. 4,330,066 (R. Berliner) a liquid receptacle in which a collapsible fluid-holding container is disposed within an outer bottle of substantially fixed shape. Unlike the box of the bag-in-box container, the outer bottle has no cracks or crevices to permit the entry of venting air between the flexible bag and the bottle as liquid is dispensed from the flexible bag. The Berliner patent teaches that the flexible bag is secured by adhesive to the bottom wall of the bottle. To vent air to the space between the flexible bag and the bottle, a plurality of apertures are formed through the thread-forming convolutions on the bottle neck. The inner container mouthpiece contains a plurality of spaced flanges which extend outwardly to snap into an annular recess formed on the inner surface of the bottle mouth. The venting air flows through the apertures and between the flanges to the air space between the collapsible bag and the bottle. A liquid receptacle having such a venting system is difficult to form and is therefore relatively expensive since venting apertures have to be formed radially through the bottle neck, and the flange-receiving annular recess must be formed on the inner surface of the bottle mouth making conventional blow forming techniques impractical. Furthermore, conventional caps are not formed to sufficiently high tolerances to seal the apertures, especially after the cap has been initially opened. This incomplete sealing can enable the flexible bag to extrude through the venting space between the flanges. Such extrusion can lead to rupture of the flexible bag and consequently to contamination of the carbonated beverage by air, whereby the beverage quickly goes flat.